The global control of tuberculosis (TB) is threatened by an increased number of multi-drug resistant TB (MDR-TB) cases and the low rates of cure achieved with current treatments. Thus, potentially useful new drugs and alternative drug delivery strategies are urgently needed. SHetA2 and OHet72 are novel anticancer drugs that also have significant activity against Mycobacterium tuberculosis, (MTB). As an alternative administration strategy, we have developed inhalable nanocrystal formulations of SHetA2 and OHet72 for delivery to the alveolar region of the lung, the main place of MTB residence. Pharmacokinetic (PK) studies of SHetA2 in mice indicated that the therapeutic dose would be larger than that of other inhalable products. OHet72 appears to be more promising since its MIC is 10-fold smaller than that of SHetA2, and PK studies in mice are ongoing. In the present application, we propose to use the guinea pig model of tuberculosis, considered the gold standard of in vivo models, to extend our preclinical studies. We will (1) Investigate the mechanism by which OHet72 kills MTB and explore possible synergy with existing anti-TB drugs in vitro, (2) Assess the pharmacokinetics of OHet72 in vivo; (3) Determine the safety of repeat pulmonary administrations of OHet72; and (4) Evaluate the efficacy of the inhaled treatment with OHet72 in the TBguinea pig model. The results of this project will be used in an R01 application to develop a platform (drug powder + inhaler) to be used in combination with selected anti-TB drugs.